Customizing your theme just got easier! The Custom CSS Upgrade now provides the ability to save revisions of your code and uses the same engine that WordPress uses for post revisions.

If you currently have the CSS upgrade, you can see this in action by logging in to your WordPress admin and going to Appearance->Edit CSS. Click the “Save Stylesheet” button. You should now see the Post Revisions box below the preview and save buttons. Note: the revisions box will appear on the CSS editing screen only after you have saved at least one revision of the CSS.
revision-metabox

If you click on one of the links in the CSS Revisions box, you will be able to visually compare different versions of your CSS.
revision-diff-cropped

If you’ve ever considered the CSS upgrade, now’s a great time to take the leap. With this new CSS revisions feature, you’ll be able to make changes  to the look of your theme without worrying about losing earlier versions, and can see how CSS changes will affect your blog’s appearance. To get the upgrade and start editing your theme’s CSS today, just log in to your WordPress.com Dashboard and click on Upgrades in the upper left menu.

*Not sure what we’re talking about? Here’s a short description of what you can and can’t do with CSS on WordPress.com.

Update:
Custom CSS will now save your preview revisions while in free trial mode. Now you can see the revisions in action before purchasing the upgrade.